As the use of smart phones, cellular telephones, and personal digital assistants, and like mobile devices in wireless communication systems continues to dramatically grow, a need exists to provide increased system performance. One technique for improving such system performance is to provide uncorrelated propagation paths using multiple-input and multiple-output (MIMO) smart antenna technology. MIMO uses multiple transmitting antennas, which are typically spatially arranged apart, at a transmitter for simultaneously transmitting spatially multiplexed signals along multiple propagation paths; and multiple receiving antennas, which are also typically spatially arranged apart, at a receiver to demultiplex the spatially multiplexed signals. MIMO technology offers significant increases in data throughput and system range without additional bandwidth or increased transceiver power by spreading the same total power over the multiple antennas. MIMO is an important part of modern wireless communication standards, such as at least one version of IEEE 802.11 (Wi-Fi), 4G, 3GPP Long Term Evolution (LTE), WiMax and HSPA+.
However, the use of multiple antennas results in an unfavorable trade-off between device size and system performance. Effective MIMO performance requires relatively high port isolation and low pattern correlation. This is typically accomplished by increasing the distance between the antennas, thereby resulting in larger devices, which are undesirable in many applications, such as handheld mobile devices or Wi-Fi access points. Although decreasing the distance between the antennas results in a desirably smaller device, it is typically obtained at the expense of higher pattern correlation, lower port isolation, and poorer performance caused by mutual coupling. Mutual coupling between the antennas typically results in wasted transmit power during transmission, and a lower received power from incoming signals during reception.
Accordingly, there is a need for a compact, multi-port, MIMO antenna with the characteristics of high port isolation and low pattern correlation for enhanced performance, as well as to a method of making such an antenna.
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The method and structural components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.